The present invention relates to a galvano-plastically produced graduation carrier comprising a plurality of fine perforations located within a perforation zone, wherein the cross-sectional profile of the graduation carrier comprises regions of depressions and/or prominences with respect to the perforation zone.
A graduation carrier is typically used in a measuring instrument to measure the relative movement of two objects movable with respect to one another. The measuring instrument frequently comprises a scanning unit and a graduation carrier. The scanning unit is connected to one of the objects and the graduation carrier is connected to the other one of the objects. As the objects move relative to one another, the graduation carrier moves relative to and is scanned by the scanning unit. Electrical signals produced by the scanning unit are indicative of the relative movement of the two objects.
The galvano-plastic process may be used to produce a thin metal coating on a specially formed base body. Briefly, the process typically involves applying a layer of photo-resist material to a base body and selectively exposing regions of the photo-resist layer to light in a manner similar to that used in the production of semiconductors. The photo-resist layer and base body are then processed such that only the portion of the base body corresponding to openings in the desired metal coating remain covered by the photo-resist layer. The processed photo-resist layer and base body are then subjected to an electrolytic process wherein the base body is connected as a cathode electrode and a metal plate as an anode electrode. An electrolytic solution is used which is preferably an acidic salt solution containing the deposit metal. The photo-resist layer and the electrolytic solution are such that the processed photo-resist layer is not damaged by the electrolytic solution. As an electric current is passed between the anode and cathode electrodes, the metal coating gradually forms on the base body. After the metal coating has reached its desired thickness it is rinsed and detached from the base body.
The use of galvano-plastically produced grid graduations in photo-electric angular motion transducers is well-known, Industrie-Anzeiger ii, 1966, No. 67, pp. 1497-1498. However, the cross-sectional profile of this type of graduation carrier is flat. Thin, flat graduation carriers have the disadvantage of poor mechanical stability. If the graduation carrier is made thicker to enhance its mechanical stability, the resolution of the graduation may be sacrificed.
The grid constant, edge sharpness, etc. of a galvano-plastically produced grid graduation is limited, as is well-known, by the resolution of the photo-resist used in the process. The thickness and therefore the corresponding stability of the graduation carrier is limited by the thickness of the photo-resist used in the galvano-plastic process. The thickness of the photo-resist and the resolution of the photo-resist are correlated in such a way that increasing the thickness of the photo-resist causes a decrease in the resolution of the photo-resist. However, decreasing the thickness of the photo-resist produces a decrease in the stability of the flat galvano-molded component.
The present invention overcomes the disadvantage of poor mechanical stability in relatively thin galvano-plastically produced graduation carriers and the disadvantage of poor grid constant and edge sharpness in relatively thick galvano-plastically produced graduation carriers.